"My Book" - Mouse Conflict?

I have just setup a "My Book" 500GB backup device and Acronis True Image 10 Home. However, I am now experiencing a very unresponsive mouse. I am using a wireless (RF) Typhoon keyboard and mouse, which has the receiver connect via USB. The "My Book" also connects via USB.

The strange this is that if I press any key on the keyboard, the mouse becomes fully responsive again for a few seconds. The only way I can now use the mouse is by pressing a key every few seconds!

I've never come across this sort of thing before, so if anyone has any advice, it would be most welcome.

BTW - the "My Book" is not backing-up when this occurs, and there seems to be no other activity using resources in any major way (CPU, Disk and Mem usage all very low).